Heat oil in a large skillet or stock pot to medium-high. Season chicken thighs with salt and pepper. Place thighs in hot oil and sear on both sides.

In a medium bowl, whisk together soy sauce, chicken broth, brown sugar, mirin, Worcestershire sauce and crushed pineapple. Stir in garlic and ginger. Pour sauce in pot with chicken. Bring to a boil, then reduce heat to medium-low; place cover on pan and cook 25-30 minutes, until chicken is tender and pulls apart easily.

Using a slotted spoon, remove chicken and place in a bowl. Turn heat to high and whisk in cornstarch/water mixture. Allow sauce to thicken, then place chicken back in the pot and coat with sauce.